Fetch blog post data from md file frontmatter

@theme/plugins/blog-posts.js

@@ -0,0 +1,130 @@
+// @ts-check
+
+import { getInnerText } from '@redocly/realm/dist/shared/markdoc.js';
+
+import { dirname, relative, join as joinPath } from 'path';
+import markdoc from '@markdoc/markdoc';
+import moment from "moment";
+
+export function blogPosts() {
+  /** @type {import("@redocly/realm/dist/server/plugins/types").PluginInstance } */
+  const instance = {
+    processContent: async (contentProvider, actions) => {
+      try {
+        const posts = [];
+        const allBlogPosts = Array.from(contentProvider.fsFilesList.values());
+
+        const markdownFiles = allBlogPosts.filter(file => file.match(/blog[\/\\]([^\\\/]*)[\/\\].*\.md$/));
+
+        for (const relativePath of markdownFiles) {
+          const record = contentProvider.loadContent(relativePath, 'frontmatter');
+          const ast = markdoc.parse(record.content);
+
+          const dirPath = dirname(relativePath);
+          const title = extractFirstHeading(ast) || '';
+          const category = extractCategory(record.parsed.data.labels);
+          const year = `${relativePath.split("/")[1]}`
+
+          posts.push({
+            path: dirPath,
+            author: record.parsed.data.author || "",
+            title: title || toTitleCase(dirname(dirPath)),
+            description: getInnerText([ast.children[1]]).replace(title, '').trim(),
+            year: year,
+            date: record.parsed.data.date
+                    ? moment(record.parsed.data.date).format("YYYY-MM-DD")
+                    : moment(year).format("YYYY-MM-DD"),
+            category: category || "none",
+            category_id: category ? category.toLowerCase().replace(/ /g, "_") : "none",
+            link: `${relativePath.replace('blog/', '').replace(".md", "")}`,
+          });
+        }
+
+        const sortedPosts = sortBlogPostsByDate(posts)
+
+        actions.createSharedData('blog-posts', { blogPosts: sortedPosts });
+        actions.addRouteSharedData('/blog/', 'blog-posts', 'blog-posts');
+      } catch (e) {
+        console.log(e);
+      }
+    },
+  };
+  return instance;
+}
+
+function extractCategory(labelsFrontmatter) {
+  const categories = [];
+  for (const i in labelsFrontmatter) {
+    if (labelsFrontmatter[i].includes("Release")) {
+      labelsFrontmatter[i] = "Release Notes"
+    }
+    categories.push(labelsFrontmatter[i]);
+  }
+  // We only need the first category from the frontmatter.
+  return categories[0];
+}
+
+function sortBlogPostsByDate(posts) {
+  const sortedItems = posts.sort((a, b) => {
+    let dateA = new Date(a.date);
+    let dateB = new Date(b.date);
+
+    // Sort in descending order
+    return dateB.getTime() - dateA.getTime();
+  });
+  return sortedItems;
+}
+
+const WORDS_TO_CAPS = ['xrp'];
+
+function toTitleCase(s) {
+  const words = s.split(/_|[^\w']/);
+  return words
+    .filter(word => word)
+    .map(word => (WORDS_TO_CAPS.includes(word) ? word.toUpperCase() : word.charAt(0).toUpperCase() + word.slice(1)))
+    .join(' ')
+    .replace("'S", "'s")
+    .replace(' A ', ' a ');
+}
+
+function unique(array) {
+  return Array.from(new Set(array));
+}
+
+function extractFirstHeading(ast) {
+  let heading;
+
+  visit(ast, node => {
+    if (!isNode(node)) {
+      return;
+    }
+
+    if (node.type === 'heading') {
+      heading = getInnerText([node]);
+      return EXIT;
+    }
+  });
+
+  return heading;
+}
+
+function isNode(value) {
+  return !!(value?.$$mdtype === 'Node');
+}
+
+const EXIT = Symbol('Exit visitor');
+function visit(node, visitor) {
+  if (!node) return;
+
+  const res = visitor(node);
+  if (res === EXIT) return res;
+
+  for (const child of node.children) {
+    if (!child || typeof child === 'string') {
+      continue;
+    }
+    const res = visit(child, visitor);
+    if (res === EXIT) return res;
+  }
+}
+